The present invention relates to an automotive suspension frame construction for supporting suspension lower arms, an engine mount member, and the like.
Generally, vehicle body constructions of a motor vehicle are broadly divided into a framed construction used for trucks etc. and a frame-less construction used for passenger cars etc. For the frame-less construction, an attempt to increase the torsional rigidity is made by incorporating side members and cross members as a part of a body instead of using a frame. Chassis parts are installed directly to the body, but on some types of vehicles, they are assembled to the body after being installed to a partial frame or a sub-frame.
This sub-frame is usually referred to as a suspension frame because the suspension lower arms are installed to both sides thereof. Hereafter, the sub-frame etc. are generally referred to as a suspension frame.
The suspension frame is fitted with the suspension lower arms, a stabilizer, and the like, and thereafter is assembled to a vehicle body. The suspension frame is generally formed by an upper plate, a lower plate, and lower arm mounting brackets, as its basic construction.
FIGS. 8 to 10 show a construction of a conventional suspension frame (Japanese Patent Provisional Publication No. 7-179180).
A suspension frame 100 is supported by a pair of side members 101, 101 on both sides, and suspension lower arms 102, 102 are installed on both sides of the suspension frame 100. A center member 104 is installed between the suspension frame 100 and a cross member 103 provided in the front, and an engine 105 is assembled onto the center member 104.
The suspension frame 100 is usually disposed at the lower part of an engine room partitioned by a dash panel 106, and various kinds of equipment etc. are assembled to the suspension frame 100. The dash panel 106 is fitted with a steering knuckle 107 by means of brackets 108.
As shown in FIGS. 11 to 13, the suspension frame 100 is formed by joining an upper plate 109 to a lower plate 110 by welding or the like. These plates 109 and 110 are usually formed by pressing a steel sheet or the like. On both sides, right and left, of the suspension frame 100, vehicle body mounting portions h, i and j for mounting the suspension frame 100 to a vehicle body are provided. On both sides in the vehicle width direction of the suspension frame 100, a pair of suspension lower arm mounting portions 100a, 100b are provided. At this suspension lower arm mounting portion 100a on the front side of the vehicle body, a lower arm mounting bracket 111 is provided in a cantilever manner.
The lower arm mounting bracket 111 is formed into a substantially square box shape with one side face being open by pressing or the like, and on opposed wall faces 111a and 111b are provided pivotally supporting portions 112, 112 for the suspension arm 102, 102. Since the lower arm mounting bracket 111 is supported in a cantilever manner on the outside of the vehicle body mounting portions h, i and j of the suspension frame 100, this configuration provides a construction that suffers disadvantages of low rigidity, decreased steering stability, and high vibrating noise.
As shown in FIG. 13, the mounting portion of the lower arm mounting bracket 111 is joined by partially lapping a distal end portion 109a of the upper plate 109 on the top face of the lower arm mounting bracket 111. Also, the distal end of the lower plate 110 is butted against the wall face of the lower arm mounting bracket 111, so that a reinforcement 113 is installed between the upper plate 109 and the lower plate 110 to reinforce the lower arm mounting bracket 111. Further, a flange portion 114 is provided along the opening end portion of the lower arm mounting bracket 111 to increase the rigidity of the lower arm mounting bracket 111.
The suspension frame 100 is subjected to the severest condition when a longitudinal load is applied (on an actual vehicle, when a brake is applied, when a wheel drops down into a pothole, or on other occasions).
The deformation mode of the suspension frame 100 at the time of braking load application is, as shown in FIG. 14, a mode in which the mounting portions of the lower arm mounting brackets 111 are opened to the outside while being twisted, and the central portion of the suspension frame 100 is lowered.
The central portion of the suspension frame 100 is lowered in the same manner when a load is applied from an engine mount member at the time of sudden start.
Conventionally, therefore, as shown in FIGS. 15 and 16, a reinforcement 115 is disposed between the upper plate 109 and the lower plate 110 to reinforce the central portion of the suspension frame 100. The upper plate 109 and the lower plate 110 are lapped on one another on the front side and form a closed curved surface on the rear side in the longitudinal direction of the vehicle body, and on the front side, the reinforcement 115 is held between the upper plate 109 and the lower plate 110, and the rear end portion of the reinforcement 115 is welded to the lower face of the closed curved surface on the rear side. Thus, engine mount member mounting portions k are formed at portions where the upper plate 109, the lower plate 110, and the reinforcement 115 are lapped on one another.
However, although the engine mount member mounting portions k are formed by lapping the upper plate 109, the lower plate 110, and the reinforcement 115 on one another, they are lowered by a load applied from the engine mount member at the time of sudden start, so that the rigidity is insufficient. Also, since the primary natural frequency of the suspension frame 100 resonates with the vehicle body, a mass damper is needed.
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide an automotive suspension frame construction that can increase the rigidity when a brake is applied or when an engine mount load is applied.
To achieve the above object, the present invention provides an automotive suspension frame construction in which an upper plate and a lower plate are joined to one another to form a suspension frame, suspension lower arm support portions are provided on each side, right and left, of the suspension frame, and an engine mount member mounting portion is provided at a substantially central portion of the suspension frame, wherein the engine mount member mounting portion of the suspension frame is formed into a closed cross section and a reinforcement is disposed in the closed cross section, cylindrical elements through which engine mount member fastening members are inserted are caused to penetrate the upper plate, reinforcement, and lower plate at positions corresponding to the engine mount member mounting portion of the suspension frame, and the upper plate, reinforcement, and lower plate are welded to the cylindrical elements.
Also, in the present invention, the reinforcement is disposed slantwise in the longitudinal direction of a vehicle body.
Further, in the present invention, a joint portion of the reinforcement and the cylindrical elements is formed into a horizontal shape.
Still further, in the present invention, the front end portion of at least the central portion of the upper plate is lowered to be joined to the front end portion of the central portion of the lower plate, and the rear end portion of at least the central portion of the lower plate is raised to be joined to the rear end portion of the central portion of the upper plate, whereby a closed cross-sectional construction is formed at the central portion of the suspension frame, and a front end flange portion of the reinforcement is joined to the front lower face of the lower plate and the rear end thereof is joined to the rear upper end of the lower plate by being butted against it.
Further, the present invention provides an automotive suspension frame construction in which an upper plate and a lower plate are joined to one another to form a suspension frame, suspension lower arm support portions are provided on each side, right and left, of the suspension frame, and an engine mount member mounting portion is provided at a substantially central portion of the suspension frame, wherein the engine mount member mounting portion of the suspension frame is formed into a closed cross section and a portion around the engine mount member mounting portion of the lower plate is formed by being raised, the raised portion is covered by a reinforcement to form a box shape, cylindrical elements through which engine mount member fastening members are inserted are caused to penetrate the upper plate, lower plate, and reinforcement at positions corresponding to the engine mount member mounting portion of the suspension frame, and the upper plate, lower plate, and reinforcement are welded to the cylindrical elements.